National Highway Traffic Safety Administration Standard 118 contains regulations to assure safe operation of power operated windows. Standard 118 has been amended to apply to power operated roof panels. It establishes requirements for power window control systems located on the vehicle exterior and for remote control devices. The purpose of the standard is to minimize the risk of personal injury that could result if a limb is caught between a closing power operated window and the window frame. The changes to Standard 118 become effective Sep. 1, 1992. Amended Standard 118 states that the maximum force allowable during an auto closure is to be less than 22 pounds onto a solid cylinder having a diameter of between 4 and 200 millimeters.
Certain problems have been identified with operation of existing power window controls. One problem is an undesirable shutdown of the power window control. It is also desirable to detect a soft obstruction in the window travel path as well as a hard obstruction. The gasket area of the window which avoids water seepage into the vehicle can present a problem to the design of a power window control, since the window or panel encounters different resistance to movement in the gasket region. An additional problem is detection of an obstruction when the motor is first activated.
Powered devices such as power windows, power seats and power doors have the potential for entrapment when operating. Entrapment, as noted above, is a safety issue that has been addressed by the National Highway Safety Administration (NHTSA Standard 118) and other agencies. For instance, sunroof panels on automobiles have been required to stop and re-open if they strike a hard cylindrical shaped object upon closure. Elevator doors are designed to re-open if an obstruction such as an arm is encountered upon closure. Domestic washing machines and dryers simply power-OFF when open in an attempt to prevent entrapment. Existing safety systems utilize contact sensors such as the movable obstruction detection panel in elevator door systems, monitoring of closure velocity (Milnes et al., U.S. Pat. No. 4,980,618) and monitoring of absolute motor current draw (Compeau et al., U.S. Pat. No. 4,823,059) among others.
Problems in the existing systems include:
1. Difficulties in detecting both hard and soft obstructions as in motor current and speed sensing. A hard obstruction such as a human head or wheel chair will cause an abrupt and easily detectable change in current draw or closure speed. A softer obstruction such as a human neck, human abdomen or a bundled child will not result in as rapid a change in current draw or closure speed. In such cases, the controller may deliver an injurious amount of closure force before the obstruction is detected, if it is detected at all. On the other hand, more sensitive controllers that sense soft obstructions can be fooled into detecting false obstructions by gradual changes in mechanical load due to wear or climate. They can also have difficulty when soft components such as flexible sealing gaskets are in the system PA0 2. Failure to hit pressure-sensing components such as the movable panel in an elevator door. A hand partially inserted into an elevator door that misses the movable elevator panel used for obstruction detection will be entrapped and can be injured if the closure force is high enough. PA0 3. Failure of passive systems such as the motor shut-off when a washing machine is in spin mode includes the fact that the tub is still spinning when opened and could still cause injury. PA0 4. Low-torque systems designed to deliver limited and safe closure force can still entrap or strangle at comparatively low-force levels or jam when closure force requirements increase due to wear.